1. Field of the Invention
The present invention generally relates to an urgent message apparatus mounted in a vehicle, for transmitting, in an emergency, an urgent message with the use of a backup battery by means of a low-earth orbit orbiting satellite, and, in particular, to an urgent message apparatus and system for appropriately warning of timing at which the backup battery should be charged or replaced.
2. Description of the Related Art
An urgent message (or a so-called mayday) apparatus and system are known in which, in an emergency, a backup battery is used, and an urgent message is transmitted with the use of cellular phone telephone network (see Japanese Laid-open Patent Applications Nos. 11-272974, 2000-231686, 2000-324039 and 2000-341196, referred to as patent documents 1 through 4, respectively, for example).
Further, an urgent message apparatus and system are known in which, in an emergency, with the use of a cellular phone instead of an in-vehicle apparatus, and an urgent message is transmitted with the use of a low-earth orbit (LEO) orbiting (not fixed) satellite communication (see Japanese Laid-open Patent Application No. 2001-250183, referred to as a patent document 5, for example).
In the low-earth orbit orbiting satellite communication, in contrast to a case of using fixed satellite communication, a time zone in which communication is not possible may occur even when an earth station is fixed at a same position on the ground, and thus, a system for providing information of a satellite communication possible time or time zone to an earth station user has been proposed (see Japanese Laid-open Patent Application No. 8-181643, referred to as a patent document 6, for example).
It is noted that, nowadays, such low-earth orbit orbiting satellite communication is actually put into a commercial use, for example, by ORBCOMM in the United States, Virginia (see Official site of ORBCOMM, URL: http://www.orbcomm.com/, Oct. 18, 2005, referred to as a non-patent document 1).